Energy storing sheet feeder

ABSTRACT

A sheet feeder includes a separation roller, a friction roller, a shaft and an energy storing element. The energy storing element stores energy when the friction roller is driven by the separation roller to rotate in the sheet-feeding direction and releases energy to make the friction roller rotate in a direction opposite to the sheet-feeding direction.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a sheet feeder, and more particularly to a sheet feeder, capable of storing energy.

2. Related Art

An automatic document feeder may be used in an image input/output apparatus, such as a scanner, a multi-function peripheral, a copier or even a printer, to feed documents or sheets one by one.

FIGS. 1 to 3 are schematic illustrations showing operations of a conventional sheet feeder. Referring to FIGS. 1 to 3, the conventional sheet feeder includes a separation roller 110, a friction roller 120 and a torque limiter 130. The separation roller 110 is mounted on a rotating shaft 112, which may be a rotating shaft of a motor. The friction roller 120 is mounted on a rotating shaft 122, which may be a rotating shaft of another motor. The torque limiter 130 connects the friction roller 120 to the rotating shaft to provide a torsional force for restricting the rotation of the friction roller 120.

As shown in FIG. 1, when the sheet-separating operation is not performed yet, the separation roller 110 rotates clockwise to rotate the friction roller 120 to feed the sheets S1 and S2, and the undesired condition of multi-sheet feeding occurs. To solve this problem, as shown in FIG. 2, the rotating shaft 122 continuously rotates the friction roller 120 clockwise through the torque limiter 130 to push the sheet S2 out of the passageway between the friction roller 120 and the separation roller 110. Thus, the sheets may be separated.

As shown in FIG. 3, when only the sheet S2 is left, the rotating shaft 112 rotates the separation roller 110 clockwise to make the sheet S2 enter the passageway, and the friction force between the sheet S2 and the friction roller 120 rotates the friction roller 120 counterclockwise while the rotating shaft 122 rotates the torque limiter 130 clockwise. However, the torque for the sheet S2 to rotate the friction roller 120 counterclockwise is larger than the torque for the torque limiter 130 to rotate the friction roller 120 clockwise. So, the sheet S2 drives the friction roller 120 to rotate counterclockwise.

Thus, the conventional sheet feeder needs two power sources and one torque limiter, and the sliding friction states are often created between the friction roller, the torque limiter and the rotating shaft. Consequently, the manufacturing cost is high and the components tend to be worn to influence the subsequent sheet-separating function.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an energy storing sheet feeder, wherein only one power source in conjunction with an energy storing element capable of storing and releasing energy are used to make the sheet-separating operation more reliable, and the cost of the sheet feeder and the wear between rollers can be reduced effectively.

To achieve the above-identified object, the invention provides an energy storing sheet feeder for feeding and separating a first sheet and a second sheet, which are stacked together. The sheet feeder includes a separation roller, a friction roller, a shaft and an energy storing element. The separation roller rotates in a sheet-feeding direction and driven by a driving device. The friction roller may be rotated by the separation roller. The shaft passes through the friction roller. The energy storing element stores energy when the friction roller is driven by the separation roller to rotate in the sheet-feeding direction and releases energy to make the friction roller rotate in a direction opposite to the sheet-feeding direction. The friction roller has a first forwarding state, a reversing state and a second forwarding state. In the first forwarding state of the friction roller, the separation roller rotates the friction roller to feed the first sheet alone or to feed the first sheet and the second sheet simultaneously, and the friction roller drives the energy storing element to make the energy storing element store the energy. In the reversing state of the friction roller, the energy storing element releases the energy to reverse the friction roller to push the second sheet away from a nip between the friction roller and the separation roller. In the second forwarding state of the friction roller, the separation roller drives the second/first sheet to make the second/first sheet rotate the friction roller and thus make the energy storing element store the energy.

According to the sheet feeder of the invention, in which the energy storage element is used to store the energy, the friction roller reverses when the energy storage element releases the energy when two sheets enter the nip between the friction roller and the separation roller. Thus, one of the sheets close to the friction roller may be ejected out of the passageway to prevent multiple sheets from being fed. It is to be noted that the energy storing element itself may have a clutch or be combined with a clutch so that the friction roller continues rotating when the energy storing element has stored the maximum energy.

Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIGS. 1 to 3 are schematic illustrations showing operations of a conventional sheet feeder.

FIGS. 4 to 7 are schematic illustrations showing operations of a sheet feeder according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.

FIGS. 4 to 7 are schematic illustrations showing operations of a sheet feeder according to a preferred embodiment of the invention. As shown in FIGS. 4 to 7, the energy storing sheet feeder according to this embodiment feeds and separates a first sheet S1 and a second sheet S2, which are stacked together. The energy storing sheet feeder includes a separation roller 10, a friction roller 20, a shaft 30 and an energy storing element 40. The separation roller 10 is driven by a rotating shaft 14 of a driving device 12 to rotate. The friction roller 20 may be rotated by the separation roller 10 as well as the first sheet S1 or the second sheet S2. The shaft 30 passes through the friction roller 20. The shaft 30 moves relative to the rotating friction roller 20 and the energy storing element 40 is disposed between the shaft 30 and the friction roller 20. Alternatively, the shaft 30 may be stationary relative to the rotating friction roller 20 and the energy storing element 40 is connected to the shaft 30. The energy storing element 40 may be a worm spring or a torsional spring. The energy storing element 40 stores energy when the friction roller 20 is driven by the separation roller 10 to rotate in the sheet-feeding direction and releases energy to make the friction roller 10 rotate in a direction opposite to the sheet-feeding direction.

In order to make the energy storing element 40 store some energy during the initial setting process, the energy storing element 40 may be preloaded to store the predetermined energy. It is to be noted that when the energy storing element 40 has stored the maximum energy, no more energy can be stored in the energy storing element 40. However, the action of the energy storing element 40 would not impede the rotation of the friction roller 20 when a mechanism, such as a one-way clutch, is used.

The friction roller 20 has a first forwarding state, a reversing state and a second forwarding state. In the first forwarding state, as shown in FIG. 4, the separation roller 10 rotating clockwise drives the friction roller 20 to rotate counterclockwise to feed the first sheet S1 or the first sheet S1 and the second sheet S2. At this time, the friction roller 20 also drives the energy storing element 40 to make the energy storing element 40 store the energy.

In the reversing state, that is, when the sheets S1 and S2 simultaneously enter a nip 60 between the friction roller 20 and the separation roller 10, as shown in FIG. 5, the energy storing element 40 releases the energy to reverse the friction roller 20 clockwise because the friction between the sheets S1 and S2 is smaller than the friction between the sheet S2 and the friction roller 20. Thus, the second sheet S2 can be pushed out of the nip 60 between the friction roller 20 and the separation roller 10, and the state shown in FIG. 6 may be obtained. When the sheet is being transported, the state may also be changed from that of FIG. 6 to that of FIG. 5. Thus, the friction roller 20 may rotate clockwise or counterclockwise intermittently to keep only one sheet in the nip 60. In other words, the energy storing element releases the energy to reverse the friction roller to push one of the sheets out of the nip as long as two sheets enter the passageway.

In the second forwarding state, as shown in FIGS. 6 and 7, the separation roller 10 drives the second/first sheet S2/S1 to make the second/first sheet S2/S1 rotate the friction roller 20 to make the energy storing element 40 store the energy.

In addition, the energy storing sheet feeder may further include a spring or a force-applying mechanism 50 of a hydraulic device, which pushes the separation roller 10 against the friction roller 20. Alternatively, the weight of the separation roller 10 may be utilized to push the separation roller 10 against the friction roller 20. Such a design makes the feeder be adapted to the sheets with various thicknesses and immediately compensates for the worn separation roller or the worn friction roller.

According to the sheet feeder of the invention, no torque limiter has to be utilized, and the energy storing element is utilized to achieve the advantage of reducing the cost and the size effectively. Because only one single power source is used, the feeder can be assembled in a simpler manner. Because rolling friction states are created between the friction roller and the separation roller and between the friction roller and the sheet, the wear of the friction roller can be effectively reduced, and the lifetime of the friction roller may be thus lengthened.

While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications. 

1. An energy storing sheet feeder for feeding and separating a first sheet and a second sheet, which are stacked together, the sheet feeder comprising: a separation roller rotating in a sheet-feeding direction and driven by a driving device; a friction roller, which may be rotated by the separation roller; a shaft, which passes through the friction roller; and an energy storing element for storing energy when the friction roller is driven by the separation roller to rotate in the sheet-feeding direction and for releasing energy to make the friction roller rotate in a direction opposite to the sheet-feeding direction.
 2. The sheet feeder according to claim 1, wherein the friction roller has a first forwarding state, a reversing state and a second forwarding state, wherein: in the first forwarding state, the separation roller rotates the friction roller to feed the first sheet alone or to feed the first sheet and the second sheet simultaneously, and the friction roller drives the energy storing element to make the energy storing element store the energy; in the reversing state, the energy storing element releases the energy to reverse the friction roller to push the second sheet away from a nip between the friction roller and the separation roller; and in the second forwarding state, the separation roller drives the second/first sheet to make the second/first sheet rotate the friction roller and thus make the energy storing element store the energy.
 3. The sheet feeder according to claim 1, wherein the shaft moves relative to the rotating friction roller and the energy storing element is disposed between the shaft and the friction roller.
 4. The sheet feeder according to claim 1, wherein the shaft is stationary relative to the rotating friction roller and the energy storing element is connected to the shaft.
 5. The sheet feeder according to claim 1, wherein the energy storing element is a worm spring or a torsional spring.
 6. The sheet feeder according to claim 5, wherein the energy storing element is preloaded to store predetermined energy in advance.
 7. The sheet feeder according to claim 1, further comprising: a force-applying mechanism for pushing the separation roller against the friction roller.
 8. The sheet feeder according to claim 7, wherein the energy storing element is a worm spring or a torsional spring.
 9. The sheet feeder according to claim 8, wherein the energy storing element is preloaded to store predetermined energy in advance. 